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  • Swifts: Nature's determined construction crew

  • Home construction is up in my neighborhood, or I should say, in my yard.
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  • Home construction is up in my neighborhood, or I should say, in my yard.
    A pair of robins is decorating a newly crafted nest with lichens taken from the maple tree. A western scrub jay just flew by with another twig to the abelia by the house. Violet-green swallows are collecting chicken feathers from a neighbor's yard to finish off their nest in a nest box.
    As expertly crafted as they are, the nests of robins, jays and swallows are not as impressive as the nest of a Vaux's swift. Weaving grass and twigs and adding a few decorations and maybe a bit of mud to make a nest is marvel enough, but the feat is much more challenging for the swift.
    First, landing on the ground to pick up a few twigs is not an option. A grounded swift is usually a dead swift. They are not equipped to launch from a flat surface. They roost and nest on vertical surfaces such as a chimney or the inside of a hollow tree that's open at the top. To become airborne, they clamber up the inside of a tree or chimney with the aid of their wings and leap into the air.
    They need space to fall until they manage flight speed. Tricky, but once in the air, they have few equals in either speed or skill.
    OK, but that leaves the problem of the nest. What do they do for building materials? The swift's solution is anything but elegant. While in full flight, the swift takes careful aim at a small dead twig high on a tree and grabs it as it flashes by. If all goes well, the twig breaks and the swift has the bird equivalent of a 2-by-4.
    What could go wrong? Well, as you might expect, not all twigs are brittle. Swifts sometimes end up hanging from a twig, willing it to break. It usually doesn't end well once that happens. Time to let go, fall, regain flight and try again. It can be worse. I have seen swifts fly at resilient twigs and end up flung backwards, tumbling in the air. Quite embarrassing, if not painful.
    As you now realize, swifts usually have to make the most of a rather meager harvest of supplies. Luckily their salivary glands are up to the task. The glands grow large with the approach of the breeding season, and the saliva becomes quite thick and sticky. It is similar to construction adhesive in texture and functions equally well. A few twigs and a healthy amount of congealed spit, and you have a nest glued to the inside of a tree or chimney suitable for five or six eggs.
    In southeast Asia, the edible-nest swiftlet (its real name) saves itself the embarrassment of harvesting twigs. Birds construct their nests in caves entirely out of molded saliva. For reasons that escape me entirely, people of the region consider a soup made from dried spit to be a delicacy. A whole industry has built up around the harvest and sale of swift nests. And apparently there is good money in this pursuit. Personally, I prefer tomato soup. It's much cheaper.
    For now, I am enjoying the show and envisioning the tidy little nest that is being constructed in my chimney, as they have been each year for many years.
    Stewart Janes is a biology professor as Southern Oregon University. He can be reached at janes@sou.edu.
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